Vibration-responsive fuel supplement valve

ABSTRACT

A diaphragm carburetor with a fuel valve controlled by a lever responsive to the position of the diaphragm with standard fuel jet and idle jet openings controlled by needle valves and an overrun protector valve to prevent engine runaway consisting of a fuel passage leading from the diaphragm chamber to the mixing passage and a ball seat in that passage with a spring-pressed ball in the seat, the spring bearing at one end on the ball and at the other end on the diaphragm lever. Thus, the spring normally acts to close the fuel valve and the ball valve but under open throttle conditions, the vibration of the engine on which the carburetor is mounted will move the ball valve from its seat and allow bleeding of fuel to the mixing passage with a consequent overrich fuel condition and slowing of the engine.

United States Patent Inventors Kenneth C. Schneider;

Charles E. Helm, both of Cm City, Mich. 3,439

Jan. 16, 1970 Aug. 24, 197 1 Walbro Corporation Cass City, Mich.

App]. No. Filed Patented Assignee vmunoN-nizsro usrvrm't snarl; EM E NT VALVE Primary Examiner-Wendell E. Burns Attorney-Barnes, Kisselle, Raisch & Choate ABSTRACT: A diaphragm carburetor with a fuel valve controlled by a lever responsive to the position of the diaphragm with standard fuel jet and idle jet openings controlled by nee die valves and an overrun protector valve to prevent engine runaway consisting of a fuel passage leading from the diaphragm chamber to the mixing passage and a ball seat in that passage with a spring-pressed ball in the seat, the spring bearing at one end on the ball and at the other end on the diaphragm lever. Thus, the spring normally acts to close the fuel valve and the ball valve but under open throttle conditions, the vibration of the engine on which the carburetor is mounted will move the ball valve from its seat and allow bleeding of fuel to the mixing passage with a consequent overrich fuel condition and slowing of the engine.

VIBRATlON-RESPONSIV E FUEL SUPPLEMENT VALVE This invention relates to a Vibration-Responsive Fuel Supplement Valve and more particularly to a carburetor to be mounted on an engine with a valve-controlled bypass to supply additional fuel under certain running conditions.

Sophisticated engine controls include a speed-responsive governor which limits the top speed but small engines used on appliances such as chain saws, because of space and cost limitations, cannot have governor equipment per se. Also, operators frequently will intentionally detach governors in order to get an engine up to speeds which are apt to be destructive. Since most engines have the carburetor attached directly thereto, the vibration of the engine is imparted to the carburetor. It is known to provide a vibration-responsive valve which admits fuel to the carburetor mixing passage to cause an over-rich condition which slows down the engine at top speeds and prevents destructive overrun.

It is an object of the present invention to provide an improved vibration-responsive valve in which the spring or resilient backup for the vibration valve also acts on the fuel supply valve, thus serving two purposes but also achieving a more responsive valve due to the inherent nature of operation of the diaphragm carburetor.

Other objects and features of the invention will be apparent in the following description and claims wherein the principles of operation of the invention are set forth together with the best mode presently contemplated for embodiment of such principles.

A drawing accompanies the disclosure and the single view shows a section of a carburetor with the principal parts displayed.

A carburetor of the general nature of the subject of the present invention is disclosed in a copending application of Charles H. Tuckey, filed Aug. 19, 1969, bearing Ser. No. 853,597. This disclosure shows a diaphragm-controlled carburetor having a main jet, idle jets, and a diaphragm acceleration pump responsive to open-throttle conditions.

In the drawing, a carburetor body has a pump cap 12 with a pumping system for fuel (not shown) which feeds fuel to passage 14 leading to a needle valve seat 16 and a needle valve 18. A diaphragm 20 held in position by plate 22 operates a pivotally mounted lever 24 which controls the opening and closing of needle valve 18. When the engine is calling for fuel because of the throttle settings, the weight of fuel in chamber 26 will decrease, the pressure in chamber 20 will also decrease, and the diaphragm will lift against the spring 30 causing valve 18 to open and allowing fuel to enter. Fuel from chamber 26 enters the mixing passage 32 through the main jet control valve 34 and the unidirectional valve 36 leading to jet An acceleration diaphragm 40 backed by a spring 42 in a chamber 44 is provided to act upon throttle opening to deliver a charge of fuel to the mixing passage in a manner defined in the previously identified Tuckey application.

It will be noted that a recess 50 is provided in the carburetor housing above the chamber 26 and above one arm of the lever 24. A valve seat cup 52 is pressed into this recess 50 with a ball seat at the top end with an opening 54. A ball 56 in the cup is retained by axial fins 58 which guide the spring 30 which seats at its top end against the ball. Fuel may flow through and around the spring. The top of chamber 50 is connected directly to the mixing passage through a passage 60.

In operation at full throttle, the engine may be running perhaps at about 8,000 to 10,000 r.p.m. drawing fuel rapidly from chamber 26 above diaphragm 20, but the vibration of the carburetor will tend to cause the ball to dance on its seat and allow fuel to pass through opening 54 into the engine. This will cause an over-rich condition which will slow down the engine and prevent it from reaching a destructive runaway condition.

It will be seen that any tendency to reduce the quantity of fuel in chamber 20 will cause lever 24 to move against the spring 30 so a built-in control is provided to keep the ball from remaining off its seat for any length of time. Thus, a balanced condition can obtain which limits the top speed of an engine without danger of a choke-kill or excessive hunting.

What is claimed as new is as follows:

1. A diaphragm carburetor for direct mount adjacent a small engine which includes a diaphragm-controlled lever actuating a fuel inlet valve comprising:

a. a carburetor body having a fuel chamber adjacent the diaphragm with a main manually adjustable jet leading from said chamber to a fuel-air-mixing passage and a fuel inlet valve operable by a fulcrummed lever responsive to said diaphragm position, said lever having a fuel inlet valve arm and a diaphragm arm on opposite sides of a fulcrum,

b. a bypass passage leading to said mixing passage from said chamber positioned to terminate adjacent the diaphragm side of said lever,

c. a valve in said bypass passage to block flow normally to said mixing passage but positioned to be responsive to vibration at a high frequency resulting from engine operation, and

d. compressing resilient means biased at one end against said valve and at the other end against said diaphragm arm of said lever wherein fuel inlet opening motion of said diaphragm increases the resilient force of said compression resilient means.

2. A diaphragm carburetor as defined in claim 1 in which said bypass passage includes a cylindrical recess having an axis substantially normal to said diaphragm, a valve seat in said recess, and said valve in said bypass passage comprises a ball valve at said seat urged on to said seat by said resilient means.

3. A diaphragm carburetor as defined in claim 1 in which said bypass passage includes a cylindrical recess having an axis substantially normal to said diaphragm, a cuplike insert in said recess having a valve seat at one end, and said valve in said bypass passage comprises a ball in said cuplike insert to close said seat urged on to said seat by said resilient means.

4. A diaphragm carburetor as defined in claim 3 in which said resilient means is a coil spring seated at one end on said ball and the other end on said diaphragm arm of said lever, and guide means in said cup to stabilize said coil spring while permitting fuel to flow therethrough. 

1. A diaphragm carburetor for direct mount adjacent a small engine which includes a diaphragm-controlled lever actuating a fuel inlet valve comprising: a. a carburetor body having a fuel chamber adjacent the diaphragm with a main manually adjustable jet leading from said chamber to a fuel-air-mixing passage and a fuel inlet valve operable by a fulcrummed lever responsive to said diaphragm position, said lever having a fuel inlet valve arm and a diaphragm arm on opposite sides of a fulcrum, b. a bypass passage leading to said mixing passage from said chamber positioned to terminate adjacent the diaphragm side of said lever, c. a valve in said bypass passage to block flow normally to said mixing passage but positioned to be responsive to vibration at a high frequency resulting from engine operation, and d. compressing resilient means biased at one end against said valve and at the other end against said diaphragm arm of said lever wherein fuel inlet opening motion of said diaphragm increases the resilient force of said compression resilient means.
 2. A diaphragm carburetor as defined in claim 1 in which said bypass passage includes a cylindrical recess having an axis substantially normal to said diaphragm, a valve seat in said recess, and said valve in said bypass passage comprises a ball valve at said seat urged on to said seat by said resilient means.
 3. A diaphragm carburetor as defined in claim 1 in which said bypass passage includes a cylindrical recess having an axis substantially normal to said diaphragm, a cuplike insert in said recess having a valve seat at one end, and said valve in said bypass passage comprises a ball in said cuplike insert to close said seat urged on to said seat by said resilient means.
 4. A diaphragm carburetor as defined in claim 3 in which said resilient means is a coil spring seated at one end on said ball and the other end on said diaphragm arm of said lever, and guide means in said cup to stabilize said coil spring while permitting fuel to flow therethrough. 